Recently, there is provided an environment in which location information of users is periodically acquired by terminals incorporating a GPS (global positioning system). Services offered by using the location information acquired by the GPS include a service for displaying a map near the user and a service which shows the way from the current location to the destination. These services are provided on the basis of the current location of the user. Provisions of further advanced services in the future have been studied, such as a service which uses user's behavior patterns extracted on the basis of the acquisition histories of the location information. Related techniques using location information are disclosed as follows:
Patent Document 1 discloses a behavior history output apparatus which can output a behavior history even by using a mobile information technology device with relatively low processing power. The behavior history output apparatus includes a location information acquisition means, a time acquisition means, a location name database, a location name retrieving means and an output means. The location information acquisition means repeatedly acquires location information at predetermined timings. The time acquisition means acquires the time when the location information is acquired. The location name database stores location names corresponding to location information. The location name retrieving means retrieves location names from the location name database on the basis of the acquired location information. The output means outputs the retrieved location names in chronological order. The behavior history output apparatus of patent document 1 enables real-time acquisition of the behavior histories even by using an information apparatus with relatively poor processing power and hardware, including a memory, such as a mobile information technology device.
Also, patent document 2 discloses a location detection method which can estimate the location of a wireless communication terminal with high accuracy. The location detection method of patent document 2 is a detection method used in a system including: a plurality of base stations connected to a communication network; a plurality of wireless communication terminals including at least a transmitting means and operating as mobile stations connected to the base stations by wireless; and an information server managing information including the location information of the wireless communication terminals. The base stations each receive wireless signals transmitted from the wireless communication terminals, and measure the reception signal levels of the received signals to inform the information server. The information server acknowledges the reception signal levels informed from the base stations, finds by using the reception signal levels the ranges where the wireless communication terminals corresponding to the reception signal levels are potentially located, and detects the locations of the wireless communication terminals on the basis of the overlapping of the respective ranges. The location detection method of patent document 2 effectively overcomes a problem that the location cannot be estimated accurately when the reception signal levels vary due to environments around the transmitting stations, and realizes a location detection system which can estimate the locations of the wireless communication terminals with high accuracy.
In patent document 1, it is presumed that the location information is acquired from the GPS with high accuracy; however, there is some uncertainty in the acquired location even when the terminal completely stands still, because the location information is calculated on the basis of the received radio waves from satellites in the GPS. To make matters worse, the accuracy of the location information becomes low, when the terminal moves or when the terminal is located underground, where the terminal cannot receive the radio waves from the satellites. Therefore, it is impossible to accurately judge whether the terminal stands still only from the coordinate value information obtained from the GPS location information, and this makes it difficult to extract the behavior pattern with high accuracy. Also, in patent document 2, the range where the terminal is potentially located can be estimated only with a certain level, although the variations in the reception signal levels from the base stations are taken into account.